This invention relates to a process for producing a printed circuit board forming a conductor circuit by electroless plating, and more particularly it relates to a printed circuit board producing process capable of accomplishing desired plating while maintaining the electroless plating solution in a stable state.
Hitherto, production of the printed circuit boards by electroless plating has comprised the following steps: (1) depositing an adhesive layer containing synthetic rubber on an insulating board, (2) roughening the deposited adhesive layer, (3) depositing a catalyst for electroless plating on the roughened surface, (4) masking the entire surface save the portion where the circuit is to be formed, and (5) performing electroless plating. This prior art process had some serious disadvantages such as unsatisfactory adhesiveness of plating film, which would cause swelling or peel-off of the plating film during soldering, and unstable electroless plating solution due to fall-off of the deposited catalyst, resulting in a reduced plating efficiency and copper utilization.
For improving such catalyst adhesiveness, it has been proposed to subject the roughened adhesive layer surface to an alkali treatment to remove the weak layer on the adhesive layer (Japanese Laid-Open Patent Publication No. 22841/1980), or to incorporate a surfactant treatment after masking to improve the partial plating quality (Japanese Laid-Open Patent Publication No. 109225/1976).